This application claims benefit of Japanese Application Nos. 2000-186664 filed on Jun. 21, 2000 and 2001-069107 filed on Mar. 12, 2001, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to an optical scanning probe device in which low-coherence light is guided and is made to exit to living-body tissue, and reflected light therefrom is guided so as to produce an optical tomogram.
2. Description of Related Art
In recent years, in the case where living-body tissue is diagnosed, in addition to an imaging device to gain optical information regarding the surface condition of the tissue, an optical CT device which can gain optical information regarding the inside of the tissue has been suggested.
In this optical CT device, picosecond pulses are used for detecting information regarding the inside of a living body and, therefore, a tomogram is produced. However, a laser light source, which emits very short-pulsed light on the order of picosecond pulse, is expensive and is large, and cumbersome handling is required.
Recently, OCT (Opticalxc2x7Coherencexc2x7Tomography) which produces a tomogram of test specimen by the use of low-coherence light has been disclosed in, for example, PCT Japanese Translation Patent Publication No. 6-511312 (U.S. Pat. No. 5,312,501).
Japanese Unexamined Patent Application Publication No. 11-56786 has disclosed in detail an optical scanning probe device which can be used by insertion through an endoscope.
However, as is shown in FIG. 4, etc., in the publication of Japanese Unexamined Patent Application Publication No. 11-56786, since the optical scanning probe device of the prior example is nearly in the shape of a cylinder, it is difficult, for example, to observe at a given distance from the living-organic tissue.
That is, it is possible to observe while the outer surface of the sheath is in contact with the surface of the living-body tissue. However, it is difficult to observe while the outer surface of the sheath is held at a position some distance from the living-body tissue surface larger than that in the aforementioned condition.
In the prior example, specifically designed optical scanning probe devices having different focus positions have been used in accordance with methods for observation and parts to be observed. Consequently, many specifically designed optical scanning probe devices have been required and therefore, a large burden has been born by the user. Furthermore, the management thereof has been cumbersome.
In the OCT device of the prior example, an observation target is radiated with a light beam for performing observation, and relative position relationship between the focus position of this light beam and the observation target is an important parameter for producing a tomogram of the OCT.
Since the beam diameter becomes minimum at the focus position of the light beam, information with the highest resolution can be gained at this part. Therefore, for example, when the focus position is located on the surface of the observation target, detailed information can be gained in the neighborhood of the surface. When the focus position is located inside the observation target, detailed information regarding the deep part can be gained.
In the case where the observation target has an intense light scattering characteristic, when the focus position coincides with the surface of the observation target, an intense light scattering occurs at the observation target surface and, therefore, only reflected light from the surface may be imaged. Consequently, it may be required that the focus position is located intentionally inside the tissue surface, or is located outside in order to observe.
Furthermore, it is important that the light beam is made to enter into the observation target as perpendicularly as possible in order to gain a tomogram with precise information regarding distance.
Japanese Unexamined Patent Application Publication No. 11-56768 has disclosed in detail an optical scanning probe device which can be used by insertion through an endoscope.
In such an optical probe device, since the light beam is made to scan in the circumferential direction in order to produce a circular tomogram centering the probe, when the observation target is located at a distance from the probe as far as possible, a wide range tomogram can be produced compared to that in the observation performed while the observation target is in contact with the probe.
Therefore, the probe, in which the focus position of the light beam has been located away from the probe, has been used, the probe has been positioned at a location some distance from the observation target, and observation has been performed while the aforementioned focus position relationship has been adjusted with the angle of the endoscope and the like.
In the case where tomography observation has been performed using an optical probe and, at the same time, endoscopic therapy has been performed from the same position by the use of endo-therapy products, for example, biopsy forceps, an endoscope having two forceps channels, etc., has been used, the optical probe has been inserted through one channel so as to observe, and an endo-therapy product such as biopsy forceps, has been inserted into the other channel so as to perform therapy aiming at the scanning position of the light beam.
However, regarding an optical probe device of a conventional example which has been inserted through an endoscope as shown in FIG. 4, etc., in the publication of Japanese Unexamined Patent Application Publication No. 11-56768, it has been very difficult to perform stable positioning while fine adjustment among the observation target, light beam focus, entry angle, etc., has been made by endoscope operation in accordance with the observation purpose in the state in which the optical probe device is protruded from the endoscope tip. In addition, it has been attended with significant difficulties to perform biopsy aiming at the scanning position of the light beam by the combination of the endoscope having two forceps channels and the biopsy forceps.
It is an object of the present invention to provide an optical scanning probe device which can perform observation while being positioned at a given distance, or the like, from the living-body tissue which becomes an observation target.
It is another object of the present invention to provide an optical scanning probe device in which the focus position can be set variably.
Other objects include that the positional relationship between the observation target and the optical probe is retained stably and, therefore, operational ease is improved, that the positional relationship between the forceps hole of the endoscope, in which an optical probe is inserted, and the positioning member is adjusted and, therefore, the probe can exhibit intrinsic optical performances, that the light beam is made to enter nearly perpendicularly into the observation target, the optical probe is precisely positioned in order to locate the focus of the light beam at a proper position in accordance with the observation purpose and, therefore, tomogram information with precise information regarding distance can be gained in accordance with the observation purpose, that biopsy is simultaneously performed with ease from the light scanning position at the same time as the tomography observation with the optical probe, that when an endoscope having one forceps channel is used, even if observation and biopsy with the optical probe cannot be performed simultaneously, marking is performed at the part observed and, therefore, biopsy is performed later using this as a landmark, that adjustment of the amount of protrusion of the probe for positioning can be performed with ease, that movement of the optical probe in the direction perpendicular to the longitudinal axis is inhibited and, therefore, the pint position of the light beam can be positioned further precisely, and that adjustment of the amount of protrusion of the optical probe for positioning can be performed with ease and, in addition to this, movement of the optical probe in the direction perpendicular to the longitudinal axis is stopped and, therefore, the pint position of the light beam can be positioned further precisely.
The above and other objects, features and advantages of the invention will become more clearly understood from the following description referring to the accompanying drawings.
An optical scanning probe device for producing an optical tomogram based on reflected light by radiating living body tissue with low-coherence light includes
a flexible sheath in which at least the tip side has excellent light transmittance,
a light exit and entrance portion which is provided in the aforementioned sheath lumen, which has an optical axis intersecting the aforementioned sheath nearly perpendicularly, and which perform exit and entrance of the light,
a housing for holding the aforementioned light exit and entrance portion,
a flexible shaft which is joined to the aforementioned housing and which transfers rotation from a driving unit at the rear end portion, and
a positioning member which is provided on the periphery of the aforementioned light exit and entrance portion and which adjusts the distance between the aforementioned living body tissue and the aforementioned light exit and entrance portion at a predetermined distance larger than the outer radius of the aforementioned sheath,
wherein the focus position of the light exiting from the aforementioned light exit-entrance portion can be adjusted in the neighborhood of the aforementioned predetermined distance by the aforementioned positioning member and, therefore, observation is performed with ease.